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>12.2. Selecting the backup medium</A
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> The most important decision regarding backups is the choice
	of backup medium.  You need to consider cost, reliability, speed,
	availability, and usability.  </P
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> Cost is important, since you should preferably have
	several times more backup storage than what you need for the data.
	A cheap medium is usually a must.  </P
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> Reliability is extremely important, since a broken
	backup can make a grown man cry.  A backup medium must be able
	to hold data without corruption for years.  The way you use the
	medium affects it reliability as a backup medium.  A hard disk
	is typically very reliable, but as a backup medium it is not
	very reliable, if it is in the same computer as the disk you
	are backing up.  </P
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> Speed is usually not very important, if backups can be done
	without interaction.  It doesn't matter if a backup takes two
	hours, as long as it needs no supervision.  On the other hand,
	if the backup can't be done when the computer would otherwise
	be idle, then speed is an issue.  </P
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> Availability is obviously necessary, since you can't
	use a backup medium if it doesn't exist.  Less obvious is the
	need for the medium to be available even in the future, and on
	computers other than your own.	Otherwise you may not be able
	to restore your backups after a disaster.  </P
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> Usability is a large factor in how often backups are made.
	The easier it is to make backups, the better.  A backup medium
	mustn't be hard or boring to use.  </P
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> The typical alternatives are floppies and tapes.
	Floppies are very cheap, fairly reliable, not very fast,
	very available, but not very usable for large amounts of data.
	Tapes are cheap to somewhat expensive, fairly reliable, fairly
	fast, quite available, and, depending on the size of the tape,
	quite comfortable.  </P
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> There are other alternatives.  They are usually not very
	good on availability, but if that is not a problem, they can
	be better in other ways.  For example, magneto-optical disks
	can have good sides of both floppies (they're random access,
	making restoration of a single file quick) and tapes (contain
	a lot of data).  </P
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